This invention relates generally to magnetic recording and reproducing, and more particularly to a floppy disc drive unit used as an auxiliary storage device of a computer.
Floppy discs are now widely used, and floppy discs on the market can be classified into two groups, one being a normal density type, and the other being a high density type. Normal density type and high density type respectively indicate the density of data to be written or recorded on a floppy disc, i.e. the amount of data written per unit area. These two types relating to data density are standardarized. Because of the difference in type, floppy discs of each type are used in particularly designed floppy disc drive units for the type. The following table shows characterstics of normal density recording and high density recording.
TABLE 1 ______________________________________ NORMAL- HIGH- ITEM DENSITY DENSITY UNIT ______________________________________ COERSIVE FORCE 300 600 Oersted MEDIUM THICKNESS 2.5 1.5 micron ROTATIONAL SPEED 300 360 rpm CUTOFF FREQ. OF LPF 300K 400K Hz RESONANT FREQ. OF 350K 500K Hz DIFFERENTIATOR AMP STORAGE CAPACITY 1 M 1.6 M byte DATA TRANSFER 250K 500K bit/s SPEED NUMBER OF TRACKS 80 70 -- ______________________________________
As will be understood from the above table, a floppy disc drive unit designed and manufactured so as to handle exclusively either normal density floppy discs or high density floppy discs cannot be used for the other type floppy discs. Therefore, two different sorts of floppy disc drive units must be prepared so that either type of floppy disc can be used. However, it is time-consuming and troublesome to change floppy disc drive units whenever different type floppy discs are used.